In most present day motor vehicles, steel sheets, shaped by a conventional deep-drawing process, are used to construct the self-supporting body structure for the motor vehicles. Girders having hollow sections are fabricated by welding together two or more deep-drawn sheets. The press tools for bending and shaping the steel sheets are relatively expensive, but they permit the production of large numbers of pressings. Thus, for large-scale production runs of vehicle bodies, steel sheets are cost-effective. However, for short production runs, the production of bodies in this way is very expensive because of the heavy investment in tooling.
From published European Patent document EP 0 146 716 BI, it is known, particularly for short production runs, to produce vehicle bodies for passenger motor vehicles having a supporting structure of hollow section frame members joined together by node elements. The hollow section frame members are formed as light-metal (e.g. aluminum alloy) extruded sections, and the node elements are formed as light-metal castings. Such supporting structures provide a more cost-effective alternative for short production runs. In addition, a construction method of this kind provides a vehicle body of lower weight and also provides improved protection against corrosion.
During a collision, the supporting structure of the vehicle body may become damaged and deformed. Generally, it is desirable to restore the vehicle body to its original condition. In the case of vehicle bodies comprised of sheet metal support structures, this restoration is relatively simple. The deformed sheet metal parts can be repaired by restraightening the deformed part on a straightening bench.
However, in the case of a vehicle body consisting of light-metal node elements and light-metal extruded sections, simply restraightening or replacing the deformed girder parts is not possible for a number of reasons. First, a deformed light-metal girder may be reshaped but only by a small amount since restraightening a bent light-metal girder by a large amount varies the structure of the girder and can result in a significant reduction in its strength. Reshaping a deformed light-metal girder on a straightening bench in the known manner for a sheet metal body is therefore impractical, ineffective, and unreliable.
It is also possible to perform a repair of a damaged girder member by cutting out and removing the entire deformed girder member and rewelding a replacement girder member in its place. Such a procedure is commonly done for the replacement of a deformed sheet metal part in a sheet metal body.
However, in view of the high temperatures produced during the welding process, such a repair procedure is not suitable for a light-metal bodywork since high temperature thermal welding adversely affects the strength of the material in the vicinity of the weld joint. This is especially critical where the heat affected zones experience repeated weldings. During the repair of a bottom sill member in light-metal bodywork, for example, a replacement sill member would be inserted between two cast light-metal node elements and fixed in place by weld seams. These weld seams would be in the immediate vicinity of the previous weld regions of the node. Thus, replacement of an entire damaged light-metal girder member at the node elements in accordance with the prior art technique would be ineffective and unreliable.
In accordance with another known repair procedure, only a portion of a girder adjacent to the region of deformation is removed and a replacement girder section is inserted in its place. The new girder section is then affixed to the remaining girder sections by "butt" welded joints. However, welding such joints, in this context, is difficult and unreliable. In addition, it is often necessary to grind down the new butt weld seams in order to restore the external surface of the newly attached girder with a smooth outer contour. Such grinding operations may adversely affect the strength and reliability of the finished joint. This procedure therefore is unacceptable in the case of frame members fabricated as light-metal extrusions. Also, for the same reasons as above described, it is very difficult and unreliable to use other types of weld joints, such as, for example, overlapping regions of the replacement girder and the original unremoved girder portions.
Therefore, there remains a need in the art for a repair technique for replacing damaged light-metal girder members of a vehicle body, whereby the deformed girder members can be repaired without compromising the original strength of the vehicle bodywork and without undue finish work.